Some values in my 'edges' don't pass check50

Question

the rightmost values in the matrix in check50 is wrong but the other values are correct. I'm not really sure what's wrong. code:

void edges(int height, int width, RGBTRIPLE image[height][width])
{
float sum_redgx, sum_greengx, sum_bluegx, sum_redgy, sum_greengy, sum_bluegy;
//temp image for storing values
RGBTRIPLE temp_img[height][width];


for (int i = 0; i < height; i++)
{
    for (int j = 0; j < width; j++)
    {
        sum_redgx = 0;
        sum_bluegx = 0;
        sum_greengx = 0;
        sum_redgy = 0;
        sum_bluegy = 0;
        sum_greengy = 0;
        
        for (int a = 0; a < 3; a++)
        {
            int iterate_i = i + blur[a];
            
            if (iterate_i < 0 || iterate_i > height - 1)
            {
                continue;
            }
            
            for (int b = 0; b < 3; b++)
            {
                int iterate_j = j + blur[b];
                if (iterate_j < 0 || iterate_j > width - 1)
                {
                    continue;
                }
                
                sum_redgx += image[iterate_i][iterate_j].rgbtRed * Gx[a][b];
                sum_greengx += image[iterate_i][iterate_j].rgbtGreen * Gx[a][b];
                sum_bluegx += image[iterate_i][iterate_j].rgbtBlue * Gx[a][b];
                sum_redgy += image[iterate_i][iterate_j].rgbtRed * Gy[a][b];
                sum_greengy += image[iterate_i][iterate_j].rgbtGreen * Gy[a][b];
                sum_bluegy += image[iterate_i][iterate_j].rgbtGreen * Gx[a][b];
            }
            
            temp_img[i][j].rgbtRed = check(round(sqrt((sum_redgx * sum_redgx) + (sum_redgy * sum_redgy))));
            temp_img[i][j].rgbtGreen = check(round(sqrt((sum_greengx * sum_greengx) + (sum_greengy * sum_greengy))));
            temp_img[i][j].rgbtBlue = check(round(sqrt((sum_bluegx * sum_bluegx) + (sum_bluegy * sum_bluegy))));
        }
    }
}

for (int i = 0; i < height; i++)
{
    for (int j = 0; j < width; j++)
    {
        image[i][j].rgbtRed = temp_img[i][j].rgbtRed;
        image[i][j].rgbtGreen = temp_img[i][j].rgbtGreen;
        image[i][j].rgbtBlue = temp_img[i][j].rgbtBlue;
    }
}
return;
}

Answer 1

I'm going to guess your check() function caps the value to 255 max. However, you store the value in your temp_img before capping it, and the RGBTRIPLE type is made up of unsigned chars which cannot hold a value over 255; consequently the values will get wrapped to incorrect ones.

Apply the check() function to the rounded value you calculate.